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Consequences of the cultivation of energy crops for the global nitrogen cycle
Ecological Applications
Abstract
In this paper, we assess the global consequences of implementing first- and second-generation bioenergy in the coming five decades, focusing on the nitrogen cycle. We use a climate mitigation scenario from the Organization for Economic Cooperation and Development's (OECD) Environmental Outlook, in which a carbon tax is introduced to stimulate production of biofuels from energy crops. In this scenario, the area of energy crops will increase from 8 Mha in the year 2000 to 270 Mha (14% of total cropland) and producing 5.6 Pg dry matter per year (12% of energy use) in 2050. This production requires an additional annual 19 Tg of N fertilizer in 2050 (15% of total), and this causes a global emission of 0.7 Tg of N2O-N (8% of agricultural emissions), 0.2 Tg NO-N (6%), and 2.2 Tg of NH3-N (5%). In addition, we project that 2.6 Tg of NO3(-)-N will leach from fields under energy crops. The emissions of N2O may be an important term in the greenhouse gas balance of biofuels produced from energy crops.
... In the scenarios where BECCS was the only land-based negative emission option 5,6 , about 128 PgC needs to be removed through BECCS to reach the temperature limiting target under Representative Concentration Pathway 2.6 (RCP 2.6). However, the real mitigation potential of BECCS depends on multiple dimensions, such as achievable bioenergy crop yields 7 , available cultivation lands 8 , land use change emissions 5,6 , and supply of water 9,10 and nutrients [11][12][13] . Marginal lands (e.g., abandoned agricultural land or degraded lands) are targeted for bioenergy crop cultivation to avoid land competition with food crops and forests 8,14,15 , but large-scale use of current agricultural systems for bioenergy crops was also proposed 12,16,17 . ...
... Therefore, there is a requirement for new trans-regional metrics to appreciate the climate impacts of BECCS and for international collaboration to share the responsibility of bioenergy crop cultivation and to address the challenges inherent in slowing down global warming by considering both the biogeochemical and biophysical effects of climate mitigation options. In addition to the biophysical effects, the feasibility of BECCS also relies on other dimensions like the related land use change carbon emissions 6 , the water demand 9,10 and the nutrient cycle [11][12][13] . A full assessment of the nexus of these aspects is thus needed. ...
... Using Eqs. (8), (11), (13), and (14), changes of air temperature change can be decomposed as: ...
Bioenergy crop with carbon capture and storage (BECCS) is a key negative emission technology to meet carbon neutrality. However, the biophysical effects of widespread bioenergy crop cultivation on temperature remain unclear. Here, using a coupled atmosphere-land model with an explicit representation of lignocellulosic bioenergy crops, we find that after 50 years of large-scale bioenergy crop cultivation following plausible scenarios, global air temperature decreases by 0.03~0.08 °C, with strong regional contrasts and interannual variability. Over the cultivated regions, woody crops induce stronger cooling effects than herbaceous crops due to larger evapotranspiration rates and smaller aerodynamic resistance. At the continental scale, air temperature changes are not linearly proportional to the cultivation area. Sensitivity tests show that the temperature change is robust for eucalypt but more uncertain for switchgrass among different cultivation maps. Our study calls for new metrics to take the biophysical effects into account when assessing the climate mitigation capacity of BECCS.
... Eleven scenarios show no change in forest area by 2050. Constant forest area from baseline to 2050 is achieved either by setting aside areas presently dominated by forest i.e. zero deforestation (Pardey et al., 2014;Bouwman et al., 2010;Erb et al., 2016) or by applying a penalty on released greenhouse gas emission in combination with 50% reduction in food waste (Stevanovic et al., 2017). Increase in forest is made possible by applying a variety of interventions in alternative scenarios (Fig. 3), which include: 1) large scale reforestation of formerly agricultural areas (Sonntag et al., 2016) including REDD-Reducing Emissions from Deforestation & Degradation (van Vuuren et al., 2017); 2) land carbon pricing (Humpenöder et al., 2015;Winchester and Reilly, 2015); 3) mitigation in land, food and bioenergy (Strapasson et al., 2017;van Vuuren et al., 2017;Sands et al., 2014;Walsh et al., 2015); 4) a combination of sustainable intensification and 50% reduction in food/agricultural waste and healthy diets (Bajželj et al., 2014); 5) high agricultural productivity growth ; and 6) conservation of protected areas/ nature parks (Kubiszewski et al., 2017). ...
... BioBaM, a biophysical accounting model (Erb et al., 2016) assumes a hypothetical zero-deforestation boundary condition for agricultural production, iAP (Pardey et al., 2014) sets aside areas presently dominated by forests that are also deemed suitable for crop production (i.e. 571 million ha) and IMAGE (Bouwman et al., 2010) implements no deforestation for bioenergy production. While these models provide compelling evidence that deforestation is not a precondition for supplying the world with sufficient food in terms of quantity and quality in 2050 (Erb et al., 2016;Pardey et al., 2014), they highlight the risk of crop and bioenergy expansion into other types of land such as savanna and grazing land (Bouwman et al., 2010;Erb et al., 2016). ...
... 571 million ha) and IMAGE (Bouwman et al., 2010) implements no deforestation for bioenergy production. While these models provide compelling evidence that deforestation is not a precondition for supplying the world with sufficient food in terms of quantity and quality in 2050 (Erb et al., 2016;Pardey et al., 2014), they highlight the risk of crop and bioenergy expansion into other types of land such as savanna and grazing land (Bouwman et al., 2010;Erb et al., 2016). ...
... (Rhoads, 2003;Saiki et al., 2014;Santiago et al., 2015). (Bouwman et al., 2010). Sais de amônio são aerossóis estáveis com tempo de vida médio de 10 dias, e são classificados como material particulado fino, MP 2.5 , com diâmetro < 2,5 µm (Allen et al., 2011;Aneja et al., 2008;Phan et al., 2013). ...
... A denitrificação é realizada por um número seleto de bactérias, trata-se do processo responsável por restituir o N 2 atmosférico. O processo é dominante em ambientes marinhos, e assim como no processo de nitrificação, o óxido nitroso é um subproduto (Bouwman et al., 2010;Canfield et al., 2010). ...
São Paulo megacity (MASP) endures recurring air quality degradation problems due to rapid industrialization and vehicular emissions. The vehicular fleet is composed of more than 6 million units, out of which, 40% of light-duty vehicles (LDVs) are equipped with flex-fuel engines burning gasohol (75% gasoline + 25% ethanol) or ethanol, and high-duty vehicles (HDVs) burning mainly diesel (5% biodiesel), which hinders physical-chemical processes involving gaseous pollutants and atmospheric aerosols. This study analyzed major inorganic compounds in particulate matter (PM2.5 and PM2.5-10), highlighting the role of nitrogen compounds, emphasizing NHx (NH3 and NH4+) in aerosol acidity and the secondary inorganic aerosol formation. Given this perspective, this research was divided in four topics: (a) ionic composition of particulate matter in road-tunnel experiments (Jânio Quadros - TJQ, and Rodoanel I - TRA); (b) statistical modeling and thermodynamic aspects; (c) evaluation of São Paulo aerosol acidity; and (d) factor emission and seasonality of ammonia in MASP The results were highlighted as follows: (i) the importance of HDV for the SO2, PM2.5-10 levels and SO42- in the water soluble fraction of PM; (ii) 30% of TJQ particulate matter total mass consist of water soluble ions, whereas in external region (of TJQ) the mean value was 55%; (iii) the predictive model [NH4+] = 0.26 + 0,37[SO42-] – 1.5[Na+] + 0.16[NO3-] + 1.9[Mg2+] could explain over 97% of ammonium inside TJQ; (iv) in the external region the chemical reaction, NH3(g) + H2O(aq) NH4+(aq) + OH-(aq), was favored due to high relative humidity levels. In contrast, (v) TJQ aerosol was mostly solid with the presence of ammonium salts; (vi) ammonium concentrations were responsible for 25% of aerosol acidity neutralization; and (vii) the average ration between ammonium and sulfate was 0.80, characterizing MASP as ammonia-limiting atmosphere. Furthermore, (viii) slope values for linear regressions between ammonia and carbon monoxide ranged between [1.2, 0.52], suggesting the importance of the NH3 vehicular emission and an association between ammonia and PM2.5 for monthly averages, suggesting the importance in the formation of secondary aerosols. Finally, (ix) we calculated the emission factor of 104 mg NH3 km-1 (tunnel experiments). In short, the present study showed the importance of ammonia in acid aerosol, its participation in the process of nucleation of PM2.5, and also its association with the vehicle fleet in MASP. The 7 Gg NHx yr-1 emission was estimated and added to other forms of reactive nitrogen deposited in lakes, rivers and other water bodies, following microbiological degradation, which may cause severe damage to theses ecosystems. Therefore, these compounds monitoring is of global concern in order to mitigate future environmental impacts.
... To estimate net C eq flux associated with bioenergy, we recommend that nitrous oxide (N 2 O) flux and carbon dioxide (CO 2 ) flux be considered. N 2 O is emitted directly from soil during both nitrification and denitrification (Bouwman et al., 2010), as well as indirectly when volatilized nitric oxide and nitrogen dioxide (NO x ) and ammonia (NH 3 ) are deposited offsite and converted to N 2 O or when leached nitrate is denitrified in waterways (Adler et al., 2007). In agricultural systems, N 2 O emissions are strongly dependent on the amount of N fertilizer applied to the soil (Crutzen et al., 2008). ...
... Ideally, local N 2 O emissions are measured empirically, but the two common methods for measuring N 2 O emissions face practical challenges: eddy covariance towers (e.g., Eugster et al., 2007) are expensive to establish and maintain, and chamber measurements are also expensive when enough chambers are used to detect the effects of "hotspots," small areas with high N 2 O emissions compared to surrounding soil (Neftel et al., 2007;Hellebrand et al., 2008). Because of these challenges, models are often used to estimate soil N 2 O flux from agronomic systems, including bioenergy production (Adler et al., 2007;Bouwman et al., 2010). The simulation model DAYCENT (Parton et al., 1998) has been used to estimate soil N 2 O flux from various bioenergy crops, using as inputs daily weather simulations, soil texture and hydraulic properties, crop growth dynamics, N application rate, harvest schedule, and tillage (Adler et al., 2007). ...
Indicators are needed to assess environmental sustainability of bioenergy systems. Effective indicators will help in the quantification of benefits and costs of bioenergy options and resource uses. We identify 19 measurable indicators for soil quality, water quality and quantity, greenhouse gases, biodiversity, air quality, and productivity, building on existing knowledge and on national and international programs that are seeking ways to assess sustainable bioenergy. Together, this suite of indicators is hypothesized to reflect major environmental effects of diverse feedstocks, management practices, and post-production processes. The importance of each indicator is identified. Future research relating to this indicator suite is discussed, including field testing, target establishment, and application to particular bioenergy systems. Coupled with such efforts, we envision that this indicator suite can serve as a basis for the practical evaluation of environmental sustainability in a variety of bioenergy systems.
... There are many greenhouse gases in the atmosphere that affect our climate. Thus, in addition to carbon dioxide (CO 2 ), the emissions of methane (CH 4 ) -the most important greenhouse gas next to CO 2 (e. g., Langeveld et al., 1997) as well the emissions of nitrous oxide (N 2 O) (e. g., Bouwman et al., 2010) -may be important factors in the greenhouse gas balance of biofuels. There are a lot of discussions on the availability of different biomass sources for bioenergy applications and on the reduction of greenhouse gas emissions compared to conventional fossil fuels. ...
... There are a lot of discussions on the availability of different biomass sources for bioenergy applications and on the reduction of greenhouse gas emissions compared to conventional fossil fuels. Emissions from cropland are high compared to grassland due to the fact that cropland (including energy crops) is generally located in areas with good soils and climatic conditions, while a major part of the global grassland area is in less favorable areas (Bouwman et al., 2010). There is much less discussion on the other effects of biomass such as the acceleration of the nitrogen cycle through increased fertilizer use resulting in losses to the environment and additional emissions of oxidized nitrogen (Erisman et al., 2010). ...
The global growth in energy demand continues, but the way of meeting rising energy needs is not sustainable. The use of biomass energy is a widely accepted strategy towards sustainable development that sees the fastest rate with the most of increase in power generation followed by strong rises in the consumption of biofuels for transport. Agriculture, forestry and wood energy sector are the leading sources of biomass for bioenergy. However, to be acceptable, biomass feedstock must be produced sustainably. Bioenergy from sustainably managed systems could provide a renewable and carbon neutral source of energy. Bioenergy systems can be relatively complex, intersectoral and site- and scale-specific. The environmental benefits of biomass-for-energy production systems can vary strongly, depending on site properties, climate, management system and input intensities. Bioenergy supply is closely linked to issues of water and land use. It is important to understand the effects of introducing it as well as it is necessary to promote integrated and synergic policies and approaches in the sectors of forestry, agriculture, energy, industry and environment. Biofuels offer attractive solutions to reducing GHG emissions, addressing energy security concerns and have also other socio-economic advantages. Currently produced biofuels are classified as first-generation. Some first-generation biofuels, such as for example ethanol from corn possibly have a limited role in the future transport fuel mix, other ones such as ethanol from sugarcane or biodiesel made from oils extracted from rerennial crops, as well as non-food and industrial crops requiring minimal input and maintenance and offering several benefits over conventional annual crops for ethanol production are promising. Sugarcane ethanol has greenhouse gas (GHG) emissions avoidance potential; can be produced sustainably; can be cost effective without governments support mechanisms, provide useful and valuable co-products; and, if carefully managed with due regard given to sustainable land use, can support the drive for sustainable development in many developing countries. Sugarcane ethanol - currently the most effective biofuel at displacing GHG emissions - is already mitigating GHGs in Brazil. Jatropha curcas L., a multipurpose, drought resistant, perennial plant has gained lot of importance for the production of biodiesel. However, it is important to point out that nearly all of studies have overstated the impacts of first-generation biofuels on global agricultural and land markets due to the fact that they have ignored the role of biofuel by-products. However, feed by-products of first-generation biofuels, such as dried distillers grains with soluble and oilseed meals are used in the livestock industry as protein and energy sources mitigates the price impacts of biofuel production as well as reduce the demand for cropland and moderate the indirect land use consequences. The production of second generation biofuels is expected to start within a few years. Many of the problems associated with first-generation biofuels can be solved by the production of second generation biofuels manufactured from abundant ligno-cellulosic materials such as cereal straw, sugar cane bagasse, forest residues, wastes and dedicated feedstocks (purpose-grown vegetative grasses, short rotation forests and other energy crops). These feedstocks are not food competitive, do not require additional agricultural land and can be grown on marginal and wasteland. Depending on the feedstock choice and the cultivation technique, second-generation biofuel production has the potential to provide benefits such as consuming waste residues and making use of abandoned land. As much as 97-98% of GHG emissions could be avoided by substituting a fossil fuel with wood fuel. Forest fertilization is an attractive option for increasing energy security and reducing net GHG emission. In addition to carbon dioxide the emissions of methane and nitrous oxides may be important factors in GHG balance of biofuels. Forest management rules, best practices for nitrogen fertilizer use and development of second generation technologies use reduce these emissions. Soils have an important role in the global budget of greenhouse gases. However, the effects of biomass production on soil properties are entirely site and practice-specific and little is known about long-term impact. Soil biological systems are resilient and they do not show any lasting impacts due to intensive site management activities. Land management practices can change dramatically the characteristic and gas exchange of an ecosystem. GHG benefits from biomass feedstock use are in some cases significantly lower if the effects of direct¹ or indirect (ILUC²) land use change are taken into account. LUC and ILUC can impact the GHG emission by affecting carbon balance in soil and thus ecosystem. To understand carbon fluxes in an ecosystem large ecosystem units and time scale are critical. Mitigation measures of the impact of land use change on greenhouse gas emissions include the use of residues as feedstock, cultivation of feedstock on abandoned arable land and use of feedstock by-products as substitutes for primary crops as animal feed. Cropping management is the other key factor in estimating GHG emissions associated with LUC and there is significant opportunity to reduce the potential carbon debt and GHG emissions through improved crop and soil management practices, including crop choice, intensity of inputs, harvesting strategy, and tilling practices. Also a system with whole trees harvesting with nutrient compensation is closely to being greenhouse-gas-neutral. Biochar applied to the soil offers a direct method for sequestrating C and generating bioenergy. However, the most recent studies showing that emissions resulting from ILUC are significant have not been systematically compared and summarized and current practices for estimating the effects of ILUC suffer from large uncertainties. Therefore, it seems to be delicate to include the ILUC effects in the GHG emission balance at a country level. The land availability is an important factor in determining bioenergy sustainability. However, even though food and biofuel/biomass can compete for land, this is not inevitably the case. The pattern of completion competition will e.g. depend on whether food security policies are in place. Moreover, the great potential for uncomplicated biomass production lies in using residues and organic waste, introduction of second generation biofuels which are more efficient in use of land and bioresources as well as restoration of degraded and wasted areas. Agroforestry has high potential for simultaneously satisfying many important objectives at ecosystems, economic and social levels. For example, as a very flexible, but low-input system, alley cropping can supply biomass resources in a sustainable way and at the same time provide ecological benefits in Central Europe. A farming system that integrates woody crops with conventional agricultural crops/pasture can more fully utilize the basic resources of water, carbon dioxide, nutrients, and sunlight, thereby producing greater total biomass yield. Overall, whether food prices will rise in parallel to an increase in biofuel demand will depend, more on trade barriers, subsidies, policies and limitations of marketing infrastructure than on lack of physical capacity. There are plant species that provide not only biofuel resources but also has the potential to sequestrate carbon to soil. For example, reed canary grass (RCG, Phalaris arundinacea L.) indicates the potential as a carbon sink. Harvest residues are increasingly utilized to produce energy. Sweden developed a series of recommendations and good-practice guidelines (GPG) for whole tree harvesting practices. Water has a multifarious relationship to energy. Biofuel production will have a relatively minor impact on the global water use. It is critically important to use low-quality water sources and to select the crops and countries that (under current production circumstances) produce bioenergy feedstock in the water-efficient way. However, local and regional impacts of biofuel production could be substantial. Knowledge of watershed characteristics, local hydrology and natural peak flow patterns coupled with site planning, location choice and species choice, are all factors that will determine whether or not this relationship is sustainable. For example, bioethanol's water requirements can range from 5 to 2138 L per liter of ethanol depending on regional irrigation practices. Moreover, sugarcane in Brazil evaporates 2,200 liters for every liter of ethanol, but this demand is met by abundant rainfall. Biomass production can have both positive and negative effects on species diversity. However, woodfuel production systems as well as agroforestry have the potential to increase biodiversity. A regional energy planning could have an important role to play in order to achieve energy-efficient and cost-efficient energy systems. Closing the loop through the optimization of all resources is essential to minimize conflicts in resource requirements as a result of increased biomass feedstock production. A systems approach where the agricultural, forestry, energy, and environmental sectors are considered as components of a single system, and environmental liabilities are used as recoverable resources for biomass feedstock production has the potential to significantly improve the economic, social, and environmental sustainability of biofuels. The LCA (life cycle analysis) approach takes into account all the input and output flows occurring in biomass production systems. The source of biomass has a big impact on LCA outcomes and there is a broad agreement in the scientific community that LCA is one of the best methodologies for the GHG balance calculation of biomass systems. Overall, maximizing benefits of bioenergy while minimizing negative impacts is most likely to occur in the presence of adequate knowledge and frameworks, such as for example certification systems, policy and guidelines. Criteria for achieving sustainability and best land use practices when producing biomass for energy must be established and adopted. ___________ ¹ Direct land-use change occurs when feedstock for biofuels purposes (e.g. soybean for biodiesel) displace a prior land-use (e.g. forest), thereby generating possible changes in the carbon stock of that land. ² Indirect land-use change (ILUC) occurs when pressure on agriculture due to the displacement of previous activity or use of the biomass induces land-use changes on other lands.
... Furthermore, land imbalances were assessed at regional level. Bouwman et al. (2010) and Pardey et al. (2014) also assumed no change in forest area, but their analyses were limited to bioenergy production and cropland expansion, respectively. More recently, Bahar et al. (2020) developed a meta-analysis aimed at assessing the impacts on forest areas by 2050 or 2100 of 63 scenarios. ...
... 8 The net amount of carbon removed by bioenergy crops depends on crop types and their yields, 9 cultivation area 10 and the CCS efficiency. 11 Bioenergy crop yields are mainly determined by the crop-type choice (which can be fast growing woody or herbaceous species 9,12 ), climatic conditions, 9 fertilization, 12,13 and water supply. 14,15 They are also associated with the spatial distribution of cultivation regions. ...
The production of bioenergy with carbon capture and storage (BECCS) is a pivotal negative emission technology. The cultivation of dedicated crops for BECCS impacts the temperature through two processes: net CO2 removal (CDR) from the atmosphere (biogeochemical cooling) and changes in the local energy balance (biophysical warming or cooling). Here, we compare the magnitude of these two processes for key grass and tree species envisioned for large-scale bioenergy crop cultivation, following economically plausible scenarios using Earth System Models. By the end of this century, the cumulative CDR from the cultivation of eucalypt (72-112 Pg C) is larger than that of switchgrass (34-83 Pg C) because of contrasting contributions of land use change carbon emissions. The combined biogeochemical and biophysical effects are cooling (-0.26 to -0.04 °C) at the global scale, but 13-28% of land areas still have net warming signals, mainly due to the spatial heterogeneity of the biophysical effects. Our study shows that the deployment of bioenergy crop cultivation should not only be guided by the principles of maximizing yield and CDR but should also take an integrated perspective that includes all relevant Earth system feedbacks.
... annually [10,11]. Agricultural soil microbial activity is driving N 2 O production [12], that is widely recognized as a major source of N 2 O, while annual 4 Tg of the total N 2 O emission from N fertilizer in croplands was reported [13]. ...
Background
Global warming caused by greenhouse gas emissions affects sustainable human development. Agricultural practices are important source of greenhouse gases (GHG). Nitrous oxide (N2O) contributes greatly to farming GHG. It is important to find a potential and practical biological technique that mitigate N2O emissions in an environment friendly way.
Methods
N2O-inhibiting fungi were isolated and identified in the lab. The fungi were added into the soil and placed in the incubator and interval gas sampling was analyzed by gas chromatograph.
Results
Fungus coding Z17 was identified molecularly with the same evolutionary branch on the phylogenetic tree with Trichoderma asperellum by BLAST comparison on NCBI GenBank. In the lab simulation, the N2O emission flux was decreased by 28.18–47.16% by inoculating Trichoderma asperellum with 10⁶ cfu·g⁻¹, 5 × 10⁶ cfu·g⁻¹ and 10⁷ cfu·g⁻¹ fungal spores in the soil compared to the control.
Conclusions
The N2O-inhibiting fungus Z17 was identified as Trichoderma asperellum, capable of suppressing N2O emissions from soil with at least 10⁶ CFU·g⁻¹ soil. The best N2O-inhibiting effect was on day 9 of inoculation into soil because most of the fungal numbers were present in soil.
Graphical Abstract
... Agriculture is one of the major sources of atmospheric N 2 O worldwide. Annual N 2 O emissions from arable soils with nitrogen (N) fertilizer input are estimated to be as much as 4 Tg (Bouwman et al., 2010), and they will contribute up to 59% of the total N 2 O emissions in 2030 (Hu et al., 2015). Therefore, it has been of increasing concern to explore strategies to mitigate N 2 O emissions from arable soils. ...
Biochar amendment has been proposed as a potential strategy to reduce soil nitrous oxide (N2O) emissions, although experimental studies have generated inconsistent results on N2O emissions following biochar amendment. Differential responses of soil N2O to biochar amendment may depend on soil microbial functional genes abundance and abiotic properties. Here we sampled three types of soil from fields under long-term cultivation of green tea (TG), film greenhouse vegetable cabbage (GV) and Jerusalem artichoke (JA), respectively. We conducted a microcosm experiment to examine N2O emissions from the different soils following biochar amendment. Results showed that biochar amendment increased N2O emissions from the GV soil while decreasing N2O emissions from the TG and JA soils in the presence of nitrogen fertilizer. Biochar amendment increased soil pH and C/N ratio across the three soils. Quantitative PCR (qPCR) analysis showed that biochar amendment also consistently increased the abundances of AOB and nosZ genes but decreased the AOA abundances for all the soils, while the effects of biochar on the abundances of nirK and nirS genes differed between the soils. Our results suggest that biochar amendment can affect the processes of both ammonia oxidation and reduction of N2O to N2 for all the soils and the net effect of biochar on N2O emissions depended on the predominant process in a specific soil. Biochar-induced increase in N2O emissions in the GV soil was largely attributed to the stimulated nitrification rate, which was primarily driven by AOB. Biochar-induced decreases in N2O emissions in the TG and JA soils were linked to the increased nosZ gene abundances. Overall, the effectiveness of biochar for mitigating N2O emissions is linked to its dominant N2O production pathway in soils.
... One, the Global Cooperation of Environmental Policy, imagines a world collaboration on environmental and other problems. Applying IMAGE and TIMER models to this scenario to investigate the consequences of biofuels production on the nitrogen cycle, Bouwman et al. (2010) demonstrated global energy crop biomass production increases from 1.7 Pg in 2030 to 5.6 Pg in 2050. In their model, agrofuels dominated until 2020, after which 2 nd -generation feedstock production from woody materials would be essential. ...
... For this study, we apply the NEWS-DIN model to simulate the dissolved inorganic nitrogen (DIN) export from the CRB as a result of human activities, natural processes, and in-stream removal processes (Dumont et al., 2005;Mayorga et al., 2010;Seitzinger et al., 2002). Nutrient loading and reservoir information used by NEWS is derived from prior global-scale analyses (Bouwman et al., 2010;Van Drecht et al., 2009). ...
Regional climate change impact (CCI) studies have widely involved
downscaling and bias correcting (BC) global climate model (GCM)-projected
climate for driving land surface models. However, BC may cause uncertainties
in projecting hydrologic and biogeochemical responses to future climate due
to the impaired spatiotemporal covariance of climate variables and a
breakdown of physical conservation principles. Here we quantify the impact
of BC on simulated climate-driven changes in water variables
(evapotranspiration (ET), runoff, snow water equivalent (SWE), and water
demand for irrigation), crop yield, biogenic volatile organic compounds
(BVOC), nitric oxide (NO) emissions, and dissolved inorganic nitrogen (DIN)
export over the Pacific Northwest (PNW) region. We also quantify the impacts
on net primary production (NPP) over a small watershed in the region (HJ-Andrews). Simulation results from the coupled ECHAM5–MPI-OM model with A1B
emission scenario were first dynamically downscaled to 12 km resolution with
the WRF model. Then a quantile-mapping-based statistical downscaling model
was used to downscale them into 1/16° resolution daily climate data
over historical and future periods. Two climate data series were generated,
with bias correction (BC) and without bias correction (NBC). Impact models
were then applied to estimate hydrologic and biogeochemical responses to
both BC and NBC meteorological data sets. These impact models include a
macroscale hydrologic model (VIC), a coupled cropping system model
(VIC-CropSyst), an ecohydrological model (RHESSys), a biogenic emissions model
(MEGAN), and a nutrient export model (Global-NEWS).
Results demonstrate that the BC and NBC climate data provide consistent
estimates of the climate-driven changes in water fluxes (ET, runoff, and
water demand), VOCs (isoprene and monoterpenes) and NO emissions, mean crop
yield, and river DIN export over the PNW domain. However, significant
differences rise from projected SWE, crop yield from dry lands, and HJ-Andrews's ET between BC and NBC data. Even though BC post-processing has no
significant impacts on most of the studied variables when taking PNW as a
whole, their effects have large spatial variations and some local areas are
substantially influenced. In addition, there are months during which BC and
NBC post-processing produces significant differences in projected changes,
such as summer runoff. Factor-controlled simulations indicate that BC
post-processing of precipitation and temperature both substantially
contribute to these differences at regional scales.
We conclude that there are trade-offs between using BC climate data for
offline CCI studies versus directly modeled climate data. These trade-offs
should be considered when designing integrated modeling frameworks for
specific applications; for example, BC may be more important when considering
impacts on reservoir operations in mountainous watersheds than when
investigating impacts on biogenic emissions and air quality, for which VOCs
are a primary indicator.
... Ammonia (NH 3 ) is an atmospheric trace alkaline gas that plays an important role in the atmospheric acidity neutralization, generating ammonium (NH 4 + ) salts which are the main secondary inorganic aerosol source (Bouwman et al. 2010;Ianniello et al. 2010;Zhang et al. 2015). Ammonium salts, considered 10-day lifetime stable aerosols, are classified as fine matter particulate, PM 2.5 , with diameter <2.5 μm (Allen et al. 2011;Aneja et al. 2008;Phan et al. 2013). ...
The main goal of this research is to evaluate the contributions of Green Chemistry as a potential tool to drive the transition to circularity. For this, we have carried out a bibliographic study, analyzing those documents, process, or experiences that dealt jointly with the Green Chemistry aspects related to circularity such circular economy, industrial ecology, and closed loop. Findings show that few authors have treated that disciplines together in the last 10 years. Based on an analysis of academic literature, common strategies (design, raw materials, life cycle assessment, processes, normative, new business, and collaboration), specific experiences (catalyst, biobased products or methods, recycling, and reusing), and difficulties to overcome (metrics, transdisciplinary research, unawareness, and competitiveness) have been identified. Finally, different kind of measures, as behind such joint metrics, informal open spaces, closer the industry, education, standards and label are proposed to facilitate the development of Green Chemistry, circular economy, industrial ecology, and closed loop with the ultimate goal of improving sustainable development.
From the evidences found, we finally conclude that it is possible to use Green Chemistry and its principles as a tool to drive the transition to circularity, being the development of open spaces for exchange information between different actors from academia, governments and regulatory actors, business and industrial sectors, with the aim of promoting disruptive advances in sustainability.
... Une grande part des incertitudes entourant ces bilans de gaz à effet de serre viennent de l'estimation des émissions de gaz à effet de serre associées à la production agricole, alors que celles-ci représentent par exemple de 34 à 44% des émissions associés à l'éthanol de maïs aux Etats-Unis (Farrell et al., 2006) et plus de 80% des émissions dans le cas des huiles végétales pures (ADEME/ DIREN, 2002). Ces incertitudes résultent principalement de la prise en compte des émissions de protoxyde d'azote (N 2 O) par les sols agricoles (Crutzen et al., 2007;Bowman et al., 2010) et de la prise en compte des émissions de dioxyde de carbone (CO 2 ) liées au possible déstockage de carbone provoqué par les changements d'usage des sols (Fargione et al., 2008;Searchinger et al., 2008;Melillo et al., 2009). Le protoxyde d'azote est naturellement produit dans les sols au cours des processus microbiens de dénitrification et nitrification. ...
Second-generation biofuels could provide renewable energy while reducing the global economy dependence on oil and mitigating climate change. However, their greenhouse gas emission balances, as well as their energy and environmental balances, are discussed, especially when they are produced from agricultural feedstock. The use of agricultural feedstock for energy purposes also raises the issue of ompetition with food production. In this context, this work contributes to the assessment of the sustainability of Miscanthus x giganteus, a perennial C4 crop candidate to the production of second-generation ethanol. The objectives of this work are (i) to achieve a multicriteria evaluation of cropping systems based on M. giganteus using data collected in farmers’ fields and (ii) to compare these cropping systems with cropping systems including other resources Agricultural candidates for biofuel production. The main contributions of this work are (i) the study of the variability of yields and winter nitrate losses in a network of commercial fields located in Burgundy (France), (ii) the characterization by modeling of M. giganteus long-term yield evolution and (iii) the integration of these findings in a process of cropping systems design and assessment aiming at comparing M. giganteus with other feedstock candidate to the production of bioethanol. The study of M. giganteus in farmers’ fields shows that the high variability of yields and
nitrate losses is linked to (i) crop age, (ii) soil type and (iii) the type of field (i.e. cultural history, size, shape, and environment). Contrasting yield scenarios, built by combining data collected in commercial fields with a long-term yield evolution model, show that the sensitivity of assessment results regarding yields depends on the assessment field. The insertion of M. giganteus in a cropping system can significantly improve the greenhouse gas emission balance as well as the environmental balance, compared with a cropping system
based on a short cropping sequence. Economic results depend strongly on M. giganteus yield. Other agricultural feedstocks are also interesting, especially on soils where the yield potential of M. giganteus is low: this is particularly the case of alfalfa stems, which can be used for second-generation ethanol production.
... Land conversion to cropping systems either through extensification or intensification of open land systems such as pasture is known to significantly increase soil organic carbon (SOC) loss (Adler et al., 2007;Zenone et al., 2011;Sanford et al., 2012). Vegetation removal and cultivation may also affect the N cycle, especially during conversion and establishment (Bouwman et al., 2010;Gelfand et al., 2011;Niki ema et al., 2012;Ruan & Robertson, 2013) and lead to significant nitrogen loss through leaching and gaseous emissions (Robertson et al., 2012;Smith et al., 2013). We must improve our understanding of N 2 O emissions of likely biofuel feedstock systems to help ensure that expansion of bioenergy production generates expected societal benefits (Robertson et al., 2008;Dale et al., 2011Dale et al., , 2014. ...
Greenhouse gas (GHG) emissions from soils are a key sustainability metric of cropping systems. During crop establishment, disruptive land-use change is known to be a critical, but under reported period, for determining GHG emissions. We measured soil N 2 O emissions and potential environmental drivers of these fluxes from a three-year establishment-phase bioenergy cropping systems experiment replicated in southcentral Wisconsin (ARL) and southwestern Michigan (KBS). Cropping systems treatments were annual monocultures (continuous corn, corn–soybean–canola rotation), perennial monocultures (switchgrass, miscanthus, and poplar), and perennial polycultures (native grass mixture, early successional community, and restored prairie) all grown using best management practices specific to the system. Cumulative three-year N 2 O emissions from annuals were 142% higher than from perennials, with fertilized perennials 190% higher than unfertilized perennials. Emissions ranged from 3.1 to 19.1 kg N 2 ON ha À1 yr À1 for the annuals with continuous corn > corn–soybean–canola rotation and 1.1 to 6.3 kg N 2 ON ha À1 yr À1 for perennials. Nitrous oxide peak fluxes typically were associated with precipitation events that closely followed fertilization. Bayesian modeling of N 2 O fluxes based on measured environmental factors explained 33% of variability across all systems. Models trained on single systems performed well in most monocultures (e.g., R 2 = 0.52 for poplar) but notably worse in polycultures (e.g., R 2 = 0.17 for early successional, R 2 = 0.06 for restored prairie), indicating that simulation models that include N 2 O emissions should be parameterized specific to particular plant communities. Our results indicate that perennial bioenergy crops in their establishment phase emit less N 2 O than annual crops, especially when not fertilized. These findings should be considered further alongside yield and other metrics contributing to important ecosystem services.
... In general, negative effects on ecosystems are related to nutrient losses to ground and surface water, uncontrolled soil erosion processes, habitat degradation and biodiversity loss, GHG emissions (mainly CO 2 and N 2 O) (Aylott and McDermott 2012). Crutzen et al. (2008) and Bouwman et al. (2010) stress that energy crops are speeding up the N cycle due to the increased application of N fertilizer, leading to emission of reactive N, including NO 3 leaching, NH 3 volatilisation and emission of N 2 O and NO. Another limiting factor for bioenergy production is the low-energy density of biomass that implies large volumes to be stocked, transported and processed in the energy plant (Elbersen et al. 2012). ...
Renewable energy sources such as biomasses can play a pivotal role to ensure security of energy supply and reduce greenhouse gases through the substitution of fossil fuels. At present, bioenergy is mainly derived from cultivated crops that mirror the environmental impacts from the intensification of agricultural systems for food production. Instead, biomass from perennial herbaceous species growing in wetland ecosystems and marginal lands has recently aroused interest as bioenergy for electricity and heat, methane and 2nd-generation bioethanol. The aim of this paper is to assess, at local scale, the energy potential of wetland vegetation growing along the minor hydrographic network of a reclamation area in Northeast Italy, by performing energy scenarios for combustion, methane and 2nd-generation ethanol. The research is based on a cross-methodology that combines survey analyses in the field with a GIS-based approach: the former consists of direct measurements and biomass sampling, the latter of spatial analyses and scaling up simulations at the minor channel network level. Results highlight that biomass from riparian zones could represent a significant source of bioenergy for combustion transformation, turning the disposal problem to cut and store in situ wetland vegetation into an opportunity to produce sustainable renewable energy at local scale.
... The projected increase for cropland is 2 million km 2 (Bruinsma 2009). Taking into account c. 3 million km 2 of land use in 2050 for bioenergy production (Bouwman et al. 2010), the 60% increase in cereal production to meet the increased food demand in 2050 has to be delivered by an increase of productivity per hectare. Between 1970 and 2010, the annual wheat productivity initially increased to a mean value of 2·5% between 1980 and 1990, but from the end of the 1980s decreased to just above 1% globally and less than 1% in Europe ( Fig. 2) and the USA (Dixon et al. 2009). ...
Current production systems for crops, meat, dairy and bioenergy in the European Union (EU) rely strongly on the external input of nitrogen (N). These systems show a high productivity per unit of land. However, the drawback is a complex web of N pollution problems contributing in a major way to degradation of ecosystems. European Union Directives and national policies have improved nutrient management and reduced fertilizer N use in most European countries, which has curbed the N pollution trends particularly in regions with high stocking rates of animals. However, improvement is slowing down and environmental targets for N are not within reach. Building on the 2011 European Nitrogen Assessment, the current paper reviews key features of the complex relationships between N use and food production in Europe in order to develop novel options for a more N-efficient, less N-polluting and secure European food system. One option is to relocate feed and livestock production from Northwestern to Central and Eastern Europe. This would allow a reduction of N rates and N pollution in cereal production in Northwest Europe by 30% (50 kg N/ha), while increasing total cereal production in Europe. Another option is a change towards legume-based cropping systems to produce animal feed, in order to decrease dependence on N fertilizer and feed imports. The greatest challenge for Europe is to decrease the demand for feed commodities, and thus for land and N, by a shift to more balanced (and healthier) diets with less animal protein. These drastic changes can be stimulated by targeted public–private research funding, while the actual implementation can be enhanced by smart payment schemes using, for example money from the Common Agricultural Policy, certification and agreements between stakeholders and players in the food and energy chain. Involving networks of consumers, producers and non-governmental organizations is critical. An effective strategy starts with convincing consumers with a Western diet to eat less meat and dairy by communicating the associated health benefits and smaller ecological footprints. Internalizing the cost of N pollution leading to increased prices for N-intensive food products may also enhance involvement of consumers and provide financial resources to compensate farmers for loss of income and extra costs for stricter N measures.
... For this study, we apply the NEWS-DIN model to simulate the dissolved inorganic nitrogen (DIN) export from the CRB as a result of human activities, natural processes, and in-stream removal processes (Dumont et al., 2005; Mayorga et al., 2010; Seitzinger et al., 2002 ). Nutrient loading and reservoir information used by NEWS is derived from prior global-scale analyses (Bouwman et al., 2010; Van Drecht et al., 2009). ...
Regional climate change impact (CCI) studies have widely involved
downscaling and bias-correcting (BC) Global Climate Model
(GCM)-projected climate for driving land surface models. However, BC may
cause uncertainties in projecting hydrologic and biogeochemical
responses to future climate due to the impaired spatiotemporal
covariance of climate variables and a breakdown of physical conservation
principles. Here we quantify the impact of BC on simulated
climate-driven changes in water variables (evapotranspiration, ET;
runoff; snow water equivalent, SWE; and water demand for irrigation),
crop yield, biogenic volatile organic compounds (BVOC), nitric oxide
(NO) emissions, and dissolved inorganic nitrogen (DIN) export over the
Pacific Northwest (PNW) Region. We also quantify the impacts on net
primary production (NPP) over a small watershed in the region (HJ
Andrews). Simulation results from the coupled ECHAM5/MPI-OM model with
A1B emission scenario were firstly dynamically downscaled to 12 km
resolutions with WRF model. Then a quantile mapping based statistical
downscaling model was used to downscale them into 1/16th degree
resolution daily climate data over historical and future periods. Two
series climate data were generated according to the option of
bias-correction (i.e. with bias-correction (BC) and without
bias-correction, NBC). Impact models were then applied to estimate
hydrologic and biogeochemical responses to both BC and NBC
meteorological datasets. These impact models include a macro-scale
hydrologic model (VIC), a coupled cropping system model (VIC-CropSyst),
an ecohydrologic model (RHESSys), a biogenic emissions model (MEGAN),
and a nutrient export model (Global-NEWS). Results
demonstrate that the BC and NBC climate data provide consistent
estimates of the climate-driven changes in water fluxes (ET, runoff, and
water demand), VOCs (isoprene and monoterpenes) and NO emissions, mean
crop yield, and river DIN export over the PNW domain. However,
significant differences rise from projected SWE, crop yield from dry
lands, and HJ Andrews's ET between BC and NBC data. Even though BC
post-processing has no significant impacts on most of the studied
variables when taking PNW as a whole, their effects have large spatial
variations and some local areas are substantially influenced. In
addition, there are months during which BC and NBC post-processing
produces significant differences in projected changes, such as summer
runoff. Factor-controlled simulations indicate that BC post-processing
of precipitation and temperature both substantially contribute to these
differences at region scales. We conclude that there are
trade-offs between using BC climate data for offline CCI studies vs.
direct modeled climate data. These trade-offs should be considered when
designing integrated modeling frameworks for specific applications;
e.g., BC may be more important when considering impacts on reservoir
operations in mountainous watersheds than when investigating impacts on
biogenic emissions and air quality (where VOCs are a primary indicator).
... Large scale land conversion to bioenergy production could have major ecological impacts [2]. Land conversion disrupts ecosystem process cycles, such as hydrology [3], soilatmospheric gas exchange [4], soil C storage [5e7] and nutrient cycles [8,9]. It also competes for land with food crops [10], affects wildlife habitat [11] and other ecosystem services, and potentially contributes to increased GHG emissions through land use change [12,13]. ...
Uncertainty exists over the magnitude of greenhouse gas (GHG) emissions associated with open land conversion to short-rotation woody biomass crops (SRWC) for bioenergy in the Northern U.S. Lake States. GHG debts incurred at the plantation establishment phase may delay the climate mitigation benefits of SRWC production. To better understand GHG debts associated with converting open lands to SRWC, we established research plantations with willow (Salix spp.), hybrid-poplar (Populus spp.), and control plots in spring 2010 at two sites in northern Michigan (ES) and Wisconsin (RH). These sites had similar climates, but differed in time since last cultivation: 5 vs. 42 years. To address the short-term effects of plantation establishment, we compared two-year biomass production and GHG emissions. We hypothesized that the long-idle ES site, with higher initial soil C and N stocks, would have higher GHG emissions following conversion compared to the recently-idle RH site, but that this would be balanced in part by greater SRWC productivity at the ES site. As hypothesized, grassland conversion resulted in two-year net GHG emissions due to land conversion of 43.21 and 33.02 Mg-CO2eq ha−1 for poplar and willow at ES that was far greater than the 4.81 and −1.54 Mg-CO2eq ha−1 for poplar and willow at RH. Contrary to our hypothesis, we did not observe greater SRWC productivity at ES, which will take longer than RH to reach C neutrality and begin mitigating GHG emissions. Our results show that site-specific soil and management factors determine the magnitude of GHG emissions.
... Understanding N cycling and demand is critical to maximizing forest production (Fisher and Binkley 2000). Over the next 40 years, the land area dedicated to bioenergy crops and subsequent fertilizer use is projected to increase nearly 33-fold and 75-fold, respectively (Bouwman et al. 2010). The selection of material for production forestry favors rapidly growing species (or genotypes within a species) with robust site requirements where net primary productivity (NPP) and nitrogen use efficiency (NUE; the amount of biomass gained per unit N acquired) increase in parallel (Ragauskas et al. 2006). ...
Background and aims Nutrient acquisition of forest stands is controlled by soil resource availability and belowground production, but tree species
are rarely compared in this regard. Here, we examine ecological and management implications of nitrogen (N) dynamics during
early forest stand development in productive commercial tree species with narrow (Populus deltoides Bartr. and Platanus occidentalis L.) and broad (Liquidambar styraciflua L. and Pinus taeda L.) site requirements while grown with a range of nutrient and water resources.
Methods We constructed N budgets by measuring N concentration ([N]) and N content (N
C
) of above- and belowground perennial and ephemeral tissues, determined N uptake (N
UP
), and calculated N use efficiency (NUE).
Results Forest stands regulated [N] within species-specific operating ranges without clear temporal or treatment patterns, thus demonstrating
equilibrium between tissue [N] and biomass accumulation. Forest stand N
C
and N
UP
increased with stand development and paralleled treatment patterns of biomass accumulation, suggesting productivity is tightly
linked to N
UP
. Inclusion of above- and belowground ephemeral tissue turnover in N
UP
calculations demonstrated that maximum N demand for narrow-sites adapted species exceeded 200 kg N ha−1 year−1 while demand for broad-site adapted species was below this level. NUE was species dependent but not consistently influenced
by N availability, suggesting relationships between NUE and resource availability were species dependent.
Conclusions Based on early stand development, species with broad site adaptability are favored for woody cropping systems because they
maintain high above- and belowground productivity with minimal fertilization requirements due to higher NUE than narrow site
adapted species.
The purpose of the work is to analyze the structure of the environmental impact of energy willow cultivation (Salix spp.) on plantations of various sizes, divided per materials and processes. The research covered 15 willow plantations, ranging from 0.31 ha to 12 ha, located in southern Poland. It was found, among others, that the so-called processes, i.e. the use of technical means of production, dominate the structure of the environmental impact (EI) related to the cultivation of energy willow, and that the cultivation of energy willow on larger plantations has a much lower environmental impact compared to cultivation on smaller plantations. Also, in the case of the environmental impact of processes, the largest environmental impact was recorded in the human health category, which is mainly associated with the consumption of fuel, i.e. diesel. It was determined, e.g., that the cultivation of energetic willow on larger plantations is characterized by a much lower environmental impact (as per the cultivation area), at approx. 108 Pt, compared to the cultivation on smaller plantations, where the value of the environmental impact is 168 Pt. A decisively dominant position in the structure of the environmental impact (EI), related to the cultivation of energy willow, is held by the so-called processes, i.e. the use of technical means of production. Their share in the total environmental impact decreases from 148.5 Pt in the group of the smallest plantations to 77.9 Pt in the group of the largest plantations.
The greater bioavailability of nitrogen (N), phosphorus (P) and potassium (K) in the Anthropocene has strongly impacted terrestrial plant communities. In northwest Europe, because high N deposition is considered the main driver of plant diversity loss, European Union (EU) legislation to reduce N deposition is expected to promote plant species recovery. However, this expectation is simplistic: it ignores the role of other macronutrients. Analysing the relationship between plant species pools and species stoichiometric niches along nutrient gradients across northern Eurasia’s herbaceous ecosystems, we found that both absolute and relative P availability are more critical than N or K availability. This result is consistent with stoichiometric niche theory, and with findings from studies of hyperdiverse forests and shrublands at lower latitudes. We show that ecosystems with low absolute and relative P availability harbour a unique set of threatened species that have narrower nutrient-based niche widths than non-threatened species. Such ecosystems represent a conservation priority, but may be further threatened by latent effects of relative P enrichment arising from reduction of N availability without simultaneous reduction of P. The narrow focus of EU legislation on reducing N, but not P, may therefore inadvertently increase the threat to many of Europe’s already threatened plant species. An EU Phosphate Directive is needed.
Bioenergy from biomass can replace fossil fuels in the production of heat, electricity, and liquid fuels for transport but the potential contribution is in need of further research and objective discussions. Biomass can also provide feedstock for the chemical industry to replace petroleum. Feedstock for this purpose are major plant oil crops such as oil palm (Elaeis guineensis or E. oleifera), soybean [Glycine max (L.) Merr.], rapeseed (Brassica napus L.), and sunflower (Helianthus annuus L.). In 2015, traditional biomass accounted for 9.1%, and biofuels for transportation accounted for 0.8% of the global final energy consumption. In principle, biomass could meet up to one-third of the projected global energy demand in 2050 by bringing new land under cultivation and/or increasing productivity. However, aside physically possible, socially acceptable biomass potential scenarios must be assessed. The main feedstocks for generating heat, electricity, or gaseous, liquid, and solid fuels are forestry, agricultural and livestock residues, short-rotation forest plantations, energy crops, and the organic component of municipal residues and wastes. Traditional biomass such as fuelwood, charcoal, and animal dung is source for about 99% of all bioenergy. Of minor importance is ‘modern’ biomass such as sugar, grain, and vegetable oil crops for the production of liquid biofuels. However, in the future the bulk of liquid biofuels may be produced from lignocellulosic crops cultivated on marginal, degraded, and surplus agricultural land. Dedicated lignocellulosic energy crops include perennial plants such as switchgrass (Panicum virgatum L.), Miscanthus x giganteus, sugarcane (Saccharum spp.), Agave spp., and short-rotation woody crops such as hybrid poplar (Populus spp.) and willow (Salix spp.). Compared to conventional crops such as corn (Zea mays L.), energy crops are less depending on favorable climatic and soil conditions and require fewer inputs of agrochemicals. Thus, using energy crops would reduce the direct competition for land with food production and ecosystem services, and potentially have lower net energy and greenhouse gas (GHG) effects. However, the carbon costs of dedicating land to bioenergy will exceed the benefits. For example, conversion of native ecosystems for bioenergy often results in soil organic carbon (SOC) loss. The long-term potential of energy crops depends largely on land availability, choice of crop species, improvements by biotechnology, water availability, and effects of climate change. Aside from the dedicated bioenergy plantations, other potential feedstocks are the large volumes of unused organic residues and wastes but it is unclear whether their share can be increased. However, agricultural residues are also required on site to maintain SOC stocks, soil health, and agricultural productivity, and to reduce soil erosion. The SOC sequestration may be the key component in determining the GHG reduction potential of biofuels compared to fossil fuels. Life cycle assessment (LCA) is a widely used approach to assess the GHG balance of biomass production. Removing 25 and 100% of corn residues, for example, jeopardizes agroecosystem services and causes losses of up to 3 and up to 8 Mg SOC ha⁻¹ in 0–30 cm soil depth after 10 years, respectively. In comparison, SOC accumulates in the top 30 cm under perennial grasses at rates of up to 1 Mg SOC ha⁻¹ yr⁻¹. Thus, more intense harvest for bioenergy adversely affects the SOC stock. Also, producing energy crop feedstock by converting previously uncultivated land will cause a reduction in the SOC stock. Otherwise, adding residues from forest harvest, processing, and after end use may be beneficial to the SOC stock compared to establishing woody crop plantations. Sugarcane, perennial grasses, and trees can be cultivated sustainably for bioenergy but estimates for the potential of global bioenergy plantations when environmental and agricultural constraints are taken into account vary widely. Specifically, long-term, large-scale biomass cultivation plots, in particular, of switchgrass and Miscanthus x giganteus are scanty. While biofuels and, in particular, liquid biofuels will offset only a modest share in fossil energy use over the next decade, the impacts on agriculture and food security may be drastic. This chapter begins with a section about biomass as feedstock alternative to petroleum. Then, agroecosystem land use and management types for producing traditional and energy crop feedstocks are discussed with a focus on non-woody plants. The chapter concludes with a section about the effects of agricultural biomass production systems for bioenergy and biofuel on SOC sequestration. Additional information about the potential of woody biomass from agroforestry and plantations as feedstock for bioenergy can be found elsewhere (e.g., Buchholz et al. 2016; Lorenz and Lal 2010).
Public policies are promoting biofuels as an alternative to fossil fuel consumption in order to mitigate greenhouse gas (GHG) emissions. However, the mitigation benefit can be at least partially compromised by emissions occurring during feedstock production. One of the key sources of GHG emissions from biofuel feedstock production, as well as conventional crops, is soil nitrous oxide (N2O), which is largely driven by nitrogen (N) management. Our objective was to determine how much GHG emissions could be reduced by encouraging alternative N management practices through application of nitrification inhibitors and a cap on N fertilization. We used the US Renewable Fuel Standards (RFS2) as the basis for a case study to evaluate technical and economic drivers influencing the N management mitigation strategies. We estimated soil N2O emissions using the DayCent ecosystem model and applied the US Forest and Agricultural Sector Optimization Model with Greenhouse Gases (FASOMGHG) to project GHG emissions for the agricultural sector, as influenced by biofuel scenarios and N management options. Relative to the current RSF2 policy with no N management interventions, results show decreases in N2O emissions ranging from 3 to 4 % for the agricultural sector (5.5-6.5 million metric tonnes CO2 eq. year−1; 1 million metric tonnes is equivalent to a Teragram) in response to a cap that reduces N fertilizer application and even larger reductions with application of nitrification inhibitors, ranging from 9 to 10 % (15.5-16.6 million tonnes CO2 eq. year−1). The results demonstrate that climate and energy policies promoting biofuel production could consider options to manage the N cycle with alternative fertilization practices for the agricultural sector and likely enhance the mitigation of GHG emissions associated with biofuels.
The environmental benefits and trade-offs of automotive biofuels are well known, but less is known about aviation biofuels. We modeled the environmental impacts of three pathways for aviation biofuel in Australia (from microalgae, pongamia, and sugarcane molasses) using attributional life cycle assessments (LCAs), applying both economic allocation and system expansion. Based on economic allocation, sugarcane molasses has the better fossil energy ratio FER (1.7 MJ out/MJ in) and GHG abatement (73% less than aviation kerosene) of the three, but with trade-offs of higher water use and eutrophication potential. Microalgae and pongamia have lower FER and GHG abatement (1.0 and 1.1; 53% and 43%), but mostly avoid eutrophication and reduce water use trade-offs. All have similar and relatively low land use intensities. If produced on land where existing carbon stocks are not compromised, the sugarcane and microalgae pathways would currently meet a 50% GHG abatement requirement. Based on system expansion, microalgae and pongamia had lower impacts than sugarcane for all categories except energy input, highlighting the positive aspects of these next-generation feedstocks. The low fossil energy conservation potential of these pathways was found to be a drawback, and significant energy efficiencies will be needed before they can affect fossil energy conservation. Energy recovery from processing residues (base case) was preferable over use as animal feed (variant case), and crucial for favorable energy and GHG conservation. However this finding is at odds with the economic preferences identified in a companion technoeconomic study.
We assessed the short-term effects of converting pastureland to hybrid poplar and willow bioenergy plantations on soil greenhouse gas (GHG) fluxes and nitrogen (N) leaching in northern Michigan, USA. We used static chambers to measure soil carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) efflux, and tension lysimeters to measure nitrate (NO3-) leaching, in newly-established poplar and willow plantation plots, and in reference pasture plots. Emissions of N2O increased markedly following cultivation with cumulative direct N2O emissions of 0.3, 4.6 and 5.9 Mg ha-1 of CO2 equivalents (CO2eq) in the reference, willow and poplar plots, respectively. Similarly, land conversion resulted in large increases of NO3- leaching with losses of 2.6, 38.8 and 53.9 kg ha-1 of N from the reference, willow and poplar plots, respectively. Soil CO2 fluxes were significantly affected by land-use conversion; soils from willow and poplar plots emitted 29-42% less CO2 relative to the reference plots. Greater root respiration in the pastureland likely explained the greater soil CO2 efflux in these plots. Estimates of the net GHG emissions due to land-use conversion were strongly influenced by assumptions regarding the root contribution (RC) to total soil CO2 efflux. Assuming an RC = 50%, we estimate that pastureland conversion at this site incurred GHG debts of 7.4 and 11.6 Mg ha-1 y-1 as CO2eq for willow and poplar, respectively, during the establishment year. These results demonstrate the need to include soil disturbance impacts on the N cycle in future life cycle assessment of these bioenergy crops
Most prior studies have found that substituting biofuels for gasoline will reduce greenhouse gases because biofuels sequester
carbon through the growth of the feedstock. These analyses have failed to count the carbon emissions that occur as farmers
worldwide respond to higher prices and convert forest and grassland to new cropland to replace the grain (or cropland) diverted
to biofuels. By using a worldwide agricultural model to estimate emissions from land-use change, we found that corn-based
ethanol, instead of producing a 20% savings, nearly doubles greenhouse emissions over 30 years and increases greenhouse gases
for 167 years. Biofuels from switchgrass, if grown on U.S. corn lands, increase emissions by 50%. This result raises concerns
about large biofuel mandates and highlights the value of using waste products.
Global nitrogen (N) budgets for intensive agricultural systems were compiled for a 0.5 by 0.5 degree resolution. These budgets include N inputs (N fertilizer, animal manure, biological N fixation and atmospheric N deposition) and outputs (N removal from the field in harvested crops and grass and grass consumption by grazing animals, ammonia volatilization, denitrification and leaching). Data for the historical years 1970 and 1995 and a projection for 2030 were used to study changes in the recovery of N and the different loss terms for intensive agricultural systems. The results indicate that the overall system N recovery and fertilizer use efficiency slowly increased in the industrialized countries between 1970 and 1995, the values for developing countries have decreased in the same period. For the coming three decades our results indicate a rapid increase in both the industrialized and developing countries. High values of > 80% for fertilizer use efficiency may be related to surface N balance deficits, implying a depletion of soil N and loss of soil fertility. The projected intensification in most developing countries will cause a gradual shift from deficits to surpluses in the coming decades. The projected fast growth of crop and livestock production, and intensification and associated increase in fertilizer inputs will cause a major increase in the surface N balance surplus in the coming three decades. This implies increasing losses of N compounds to air (ammonia, nitrous oxide and nitric oxide), and groundwater and surface water (nitrate).
We present a global model that describes the fate of nitrogen (N) from point and nonpoint sources in the hydrological system up to the river mouths at the 0.5° by 0.5° spatial and annual temporal resolution. Estimates for point sources are based on population densities, per capita human N emissions, and data on sanitation coverage and wastewater treatment. For nonpoint sources, we use spatial information on land use, climate, hydrology, geology, and soils, combined with data on N inputs (fertilizers and animal manure, biological N fixation, and atmospheric deposition), and outputs (N removal in harvested agricultural products, ammonia emissions). Denitrification in the root zone and nitrate leaching to groundwater are calculated with a model that combines the effect of temperature, crop type, soil properties, and hydrological conditions. The nitrate concentration of the outflow for shallow and deep groundwater layers is based on historical inputs of fertilizer N and the effects of residence time and denitrification. In-stream N retention is based on a global estimate of 30% of the N discharged to surface water. Calculated and reported total N concentrations of discharge near the river outlet agree fairly well. However, our model systematically overestimates total N concentrations for river basins with mean annual temperature >0°C.
One of the main causes of the low efficiency in nitrogen (N) use by crops is the volatilization of ammonia (NH3) from fertilizers. Information taken from 1667 NH3 volatilization measurements documented in 148 research papers was summarized to assess the influence on NH3 volatilization of crop type, fertilizer type, and rate and mode of application and temperature, as well as soil organic carbon, texture, pH, CEC, measurement technique, and measurement location. The data set was summarized in three ways: (1) by calculating means for each of the factors mentioned, in which findings from each research paper were weighted equally; (2) by calculating weighted median values corrected for unbalanced features of the collected data; and (3) by developing a summary model using linear regression based on weighted median values for NH3 volatilization and by calculating global NH3 volatilization losses from fertilizer application using 0.5 resolution data on land use and soils. The calculated median NH3 loss from global application of synthetic N fertilizers (78 million tons N per year) and animal manure (33 million tons N per year) amount to 14 (1019) and 23 (1929), respectively. In developing countries, because of high temperatures and the widespread use of urea, ammonium sulfate, and ammonium bicarbonate, estimated NH3 volatilization loss from synthetic fertilizers amounts to 18, and in industrialized countries it amounts to 7. The estimated NH3 loss from animal manure is 21 in industrialized and 26 in developing countries.
This book (Milieu- en Natuurplanbureau) concentrates on the data and models used in IMAGE 2.4, illustrated with a number of applications
Information from 846 N2O emission measurements in agricultural fields and 99 measurements for NO emissions was used to describe the influence of various factors regulating emissions from mineral soils in models for calculating global N2O and NO emissions. Only those factors having a significant influence on N2O and NO emissions were included in the models. For N2O these were (1) environmental factors (climate, soil organic C content, soil texture, drainage and soil pH); (2) management-related factors (N application rate per fertilizer type, type of crop, with major differences between grass, legumes and other annual crops); and (3) factors related to the measurements (length of measurement period and frequency of measurements). The most important controls on NO emission include the N application rate per fertilizer type, soil organic-C content and soil drainage. Calculated global annual N2O-N and NO-N emissions from fertilized agricultural fields amount to 2.8 and 1.6 Mtonne, respectively. The global mean fertilizer-induced emissions for N2O and NO amount to 0.9 and 0.7, respectively, of the N applied. These overall results account for the spatial variability of the main N2O and NO emission controls on the landscape scale.
The carbon sequestered by restoring forests is greater than the emissions avoided by the use of the liquid biofuels. Choosing from among the host of strategies for mitigation of anthropogenic carbon emissions is not easy. There are competing environmental priorities, social and economic factors, and commercial and political interests. One strategy that has received extensive attention is the use of biofuels for transport, particularly ethanol from fermentation of carbohydrate crops as a substitute for petrol and vegetable oils in place of diesel fuel. Such an approach would require very large areas of land in order to make a significant
n this study, we analyze the impact of fertilizer- and manure-induced N2O emissions due to energy crop production on the reduction of greenhouse gas (GHG) emissions when conventional transportation fuels are replaced by first-generation biofuels (also taking account of other GHG emissions during the entire life cycle). We calculate the nitrous oxide (N2O) emissions by applying a statistical model that uses spatial data on climate and soil. For the land use that is assumed to be replaced by energy crop production (the 'reference land-use system'), we explore a variety of options, the most important of which are cropland for food production, grassland, and natural vegetation. Calculations are also done in the case that emissions due to energy crop production are fully additional and thus no reference is considered. The results are combined with data on other emissions due to biofuels production that are derived from existing studies, resulting in total GHG emission reduction potentials for major biofuels compared with conventional fuels. The results show that N2O emissions can have an important impact on the overall GHG balance of biofuels, though there are large uncertainties. The most important ones are those in the statistical model and the GHG emissions not related to land use. Ethanol produced from sugar cane and sugar beet are relatively robust GHG savers: these biofuels change the GHG emissions by ¿103% to ¿60% (sugar cane) and ¿58% to ¿17% (sugar beet), compared with conventional transportation fuels and depending on the reference land-use system that is considered. The use of diesel from palm fruit also results in a relatively constant and substantial change of the GHG emissions by ¿75% to ¿39%. For corn and wheat ethanol, the figures are ¿38% to 11% and ¿107% to 53%, respectively. Rapeseed diesel changes the GHG emissions by ¿81% to 72% and soybean diesel by ¿111% to 44%. Optimized crop management, which involves the use of state-of-the-art agricultural technologies combined with an optimized fertilization regime and the use of nitrification inhibitors, can reduce N2O emissions substantially and change the GHG emissions by up to ¿135 percent points (pp) compared with conventional management. However, the uncertainties in the statistical N2O emission model and in the data on non-land-use GHG emissions due to biofuels production are large; they can change the GHG emission reduction by between ¿152 and 87 pp.
The number of published N2O and NO emissions measurements is increasing steadily, providing additional information about driving factors of these emissions and allowing an improvement of statistical N-emission models. We summarized information from 1008 N2O and 189 NO emission measurements for agricultural fields, and 207 N2O and 210 NO measurements for soils under natural vegetation. The factors that significantly influence agricultural N2O emissions were N application rate, crop type, fertilizer type, soil organic C content, soil pH and texture, and those for NO emissions include N application rate, soil N content and climate. Compared to an earlier analysis the 20% increase in the number of N2O measurements for agriculture did not yield more insight or reduced uncertainty, because the representation of environmental and management conditions in agro-ecosystems did not improve, while for NO emissions the additional measurements in agricultural systems did yield a considerable improvement. N2O emissions from soils under natural vegetation are significantly influenced by vegetation type, soil organic C content, soil pH, bulk density and drainage, while vegetation type and soil C content are major factors for NO emissions. Statistical models of these factors were used to calculate global annual emissions from fertilized cropland (3.3 Tg N2O-N and 1.4 Tg NO-N) and grassland (0.8 Tg N2O-N and 0.4 Tg NO-N). Global emissions were not calculated for soils under natural vegetation due to lack of data for many vegetation types
The relationship, on a global basis, between the amount of N fixed by chemical, biological or atmospheric processes entering the terrestrial biosphere, and the total emission of nitrous oxide (N<sub>2</sub>O), has been re-examined, using known global atmospheric removal rates and concentration growth of N<sub>2</sub>O as a proxy for overall emissions. The relationship, in both the pre-industrial period and in recent times, after taking into account the large-scale changes in synthetic N fertiliser production and deforestation, is consistent, showing an overall conversion factor of 3–5%. This factor is covered only in part by the ~1% of "direct" emissions from agricultural crop lands estimated by IPCC (2006), or the "indirect" emissions cited therein. This means that the extra N<sub>2</sub>O entering the atmosphere as a result of using N to produce crops for biofuels will also be correspondingly greater than that estimated just on the basis of IPCC (2006). When the extra N<sub>2</sub>O emission from biofuel production is calculated in "CO<sub>2</sub>-equivalent" global warming terms, and compared with the quasi-cooling effect of "saving" emissions of fossil fuel derived CO<sub>2</sub>, the outcome is that the production of commonly used biofuels, such as biodiesel from rapeseed and bioethanol from corn (maize), can contribute as much or more to global warming by N<sub>2</sub>O emissions than cooling by fossil fuel savings. Crops with less N demand, such as grasses and woody coppice species have more favourable climate impacts. This analysis only considers the conversion of biomass to biofuel. It does not take into account the use of fossil fuel on the farms and for fertilizer and pesticide production, but it also neglects the production of useful co-products. Both factors partially compensate each other. This needs to be analyzed in a full life cycle assessment.
The relationship, on a global basis, between the amount of N fixed by chemical, biological or atmospheric processes entering the terrestrial biosphere, and the total emission of nitrous oxide (N<sub>2</sub>O), has been re-examined, using known global atmospheric removal rates and concentration growth of N<sub>2</sub>O as a proxy for overall emissions. For both the pre-industrial period and in recent times, after taking into account the large-scale changes in synthetic N fertiliser production, we find an overall conversion factor of 3–5% from newly fixed N to N<sub>2</sub>O-N. We assume the same factor to be valid for biofuel production systems. It is covered only in part by the default conversion factor for "direct" emissions from agricultural crop lands (1%) estimated by IPCC (2006), and the default factors for the "indirect" emissions (following volatilization/deposition and leaching/runoff of N: 0.35–0.45%) cited therein. However, as we show in the paper, when additional emissions included in the IPCC methodology, e.g. those from livestock production, are included, the total may not be inconsistent with that given by our "top-down" method. When the extra N<sub>2</sub>O emission from biofuel production is calculated in "CO<sub>2</sub>-equivalent" global warming terms, and compared with the quasi-cooling effect of "saving" emissions of fossil fuel derived CO<sub>2</sub>, the outcome is that the production of commonly used biofuels, such as biodiesel from rapeseed and bioethanol from corn (maize), depending on N fertilizer uptake efficiency by the plants, can contribute as much or more to global warming by N<sub>2</sub>O emissions than cooling by fossil fuel savings. Crops with less N demand, such as grasses and woody coppice species, have more favourable climate impacts. This analysis only considers the conversion of biomass to biofuel. It does not take into account the use of fossil fuel on the farms and for fertilizer and pesticide production, but it also neglects the production of useful co-products. Both factors partially compensate each other. This needs to be analyzed in a full life cycle assessment.
Humans continue to transform the global nitrogen cycle at a record pace, reflecting an increased combustion of fossil fuels,
growing demand for nitrogen in agriculture and industry, and pervasive inefficiencies in its use. Much anthropogenic nitrogen
is lost to air, water, and land to cause a cascade of environmental and human health problems. Simultaneously, food production
in some parts of the world is nitrogen-deficient, highlighting inequities in the distribution of nitrogen-containing fertilizers.
Optimizing the need for a key human resource while minimizing its negative consequences requires an integrated interdisciplinary
approach and the development of strategies to decrease nitrogen-containing waste.
This book is an atmospheric-science text for undergraduate science majors which can be used for further study by more advanced practitioners. The subject matter is approached from the perspective of atmospheric chemistry. Nineteen chapters, each with exercises at the end are included. Topics cover the following general subject areas: basic processes that create a global environment; budgets, cycles and modeling approaches to environmental understanding; future projections, both specific and general.
The number of published N2O and NO emissions measurements is increasing steadily, providing additional information about driving factors of these emissions and allowing an improvement of statistical N-emission models. We summarized information from 1008 N2O and 189 NO emission measurements for agricultural fields, and 207 N2O and 210 NO measurements for soils under natural vegetation. The factors that significantly influence agricultural N2O emissions were N application rate, crop type, fertilizer type, soil organic C content, soil pH and texture, and those for NO emissions include N application rate, soil N content and climate. Compared to an earlier analysis the 20% increase in the number of N2O measurements for agriculture did not yield more insight or reduced uncertainty, because the representation of environmental and management conditions in agro-ecosystems did not improve, while for NO emissions the additional measurements in agricultural systems did yield a considerable improvement. N2O emissions from soils under natural vegetation are significantly influenced by vegetation type, soil organic C content, soil pH, bulk density and drainage, while vegetation type and soil C content are major factors for NO emissions. Statistical models of these factors were used to calculate global annual emissions from fertilized cropland (3.3 Tg N2O-N and 1.4 Tg NO-N) and grassland (0.8 Tg N2O-N and 0.4 Tg NO-N). Global emissions were not calculated for soils under natural vegetation due to lack of data for many vegetation types.
Cited By (since 1996):1, Export Date: 5 June 2013, Source: Scopus
This volume of the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) provides a comprehensive, state-of-the-art and worldwide overview of scientific knowledge related to the mitigation of climate change. It includes a detailed assessment of costs and potentials of mitigation technologies and practices, implementation barriers, and policy options for the sectors: energy supply, transport, buildings, industry, agriculture, forestry and waste management. It links sustainable development policies with climate change practices. This volume will again be the standard reference for all those concerned with climate change. Contents: Foreword; Preface; Summary for policymakers; Technical Summary; 1. Introduction; 2. Framing issues; 3. Issues related to mitigation in the long term context; 4. Energy supply; 5. Transport and its infrastructure; 6. Residential and commercial buildings; 7. Industry; 8. Agriculture; 9. Forestry; 10. Waste management; 11. Mitigation from a cross sectoral perspective; 12. Sustainable development and mitigation; 13. Policies, instruments and co-operative agreements. 300 figs., 50 tabs., 3 annexes.
Before new technologies enter the market, their environmental superiority over competing options must be asserted based on a life cycle approach. However, when applying the prevailing status-quo Life Cycle Assessment (LCA) approach to future renewable energy systems, one does not distinguish between impacts which are ‘imported’ into the system due to the ‘background system’ (e.g. due to supply of materials or final energy for the production of the energy system), and what is the improvement potential of these technologies compared to competitors (e.g. due to process and system innovations or diffusion effects). This paper investigates a dynamic approach towards the LCA of renewable energy technologies and proves that for all renewable energy chains, the inputs of finite energy resources and emissions of greenhouse gases are extremely low compared with the conventional system. With regard to the other environmental impacts the findings do not reveal any clear verdict for or against renewable energies.Future development will enable a further reduction of environmental impacts of renewable energy systems. Different factors are responsible for this development, such as progress with respect to technical parameters of energy converters, in particular, improved efficiency; emissions characteristics; increased lifetime, etc.; advances with regard to the production process of energy converters and fuels; and advances with regard to ‘external’ services originating from conventional energy and transport systems, for instance, improved electricity or process heat supply for system production and ecologically optimized transport systems for fuel transportation.The application of renewable energy sources might modify not only the background system, but also further downstream aspects, such as consumer behavior. This effect is, however, strongly context and technology dependent.
The availability of the resources is an important factor for high shares of biomass to penetrate the electricity, heat or liquid fuel markets. We have analysed the geographical and technical potential of energy crops for the years 2050–2100 for three land-use categories: abandoned agricultural land, low-productivity land and ‘rest land’, i.e. remaining no-productive land. We envisaged development paths using four scenarios resulting from different future land-use patterns that were developed by the Intergovernmental Panel on Climate Change in its Special Report on Emission Scenarios: A1, A2, B1 and B2. The geographical potential is defined as the product of the available area for energy crops and the corresponding productivity level for energy crops. The geographical potential of abandoned agricultural land is the largest contributor. For the year 2050 the geographical potential of abandoned land ranges from about 130 to 410 EJ yr−1. For the year 2100 it ranges from 240 to 850 EJ yr−1. The potential of low-productive land is negligible compared to the other categories. The rest land area is assumed to be partly available, resulting in ranges of the geographical potential from about 35 to 245 EJ yr−1 for the year 2050 and from about 35 to 265 EJ yr−1 in 2100. At a regional level, significant potentials are found in the Former USSR, East Asia and South America. The geographical potential can be converted to transportation fuels or electricity resulting in ranges of the technical potential for fuels in the year 2050 and 2100 equal to several times the present oil consumption.
An estimate of net carbon (C) pool changes and long-term C sequestration in trees and soils was made at more than 100 intensively monitored forest plots (level II plots) and scaled up to Europe based on data for more than 6000 forested plots in a systematic 16 km x 16 km grid (level I plots). C pool changes in trees at the level II plots were based on repeated forest growth surveys At the level I plots, an estimate of the mean annual C pool changes was derived from stand age and available site quality characteristics. C sequestration, being equal to the long-term C pool changes accounting for CO2 emissions because of harvest and forest fires, was assumed 33% of the overall C pool changes by growth. C sequestration in the soil were based on calculated nitrogen (N) retention (N deposition minus net N uptake minus N leaching) rates in soils, multiplied by the C/N ratio of the forest soils, using measured data only (level II plots) or a combination of measurements and model calculations (level I plots). Net C sequestration by forests in Europe (both trees and soil) was estimated at 0.117 Gton yr(-1), with the C sequestration in stem wood being approximately four times as high (0.094 Gton yr(-1)) as the C sequestration in the soil (0.023 Gton yr(-1)). The European average impact of an additional N input on the net C sequestration was estimated at approximately 25 kg C kg(-1) N for both tree wood and soil. The contribution of an average additional N deposition on European forests of 2.8 kg ha(-1) yr(-1) in the period 1960-2000 was estimated at 0.0118 Gton yr(-1), being equal to 10% of the net C sequestration in both trees and soil in that period (0.117 Gton yr(-1)). The C sequestration in trees increased from Northern to Central Europe, whereas the C sequestration in soil was high in Central Europe and low in Northern and Southern Europe. The result of this study implies that the impact of forest management on tree growth is most important in explaining the C pool changes in European forests.
The Integrated Model to Assess the Global Environment (IMAGE) is a dynamic integrated assessment modelling framework for global change. The main objectives of IMAGE are to contribute to scientific understanding and support decision-making by quantifying the relative importance of major processes and interactions in the society-biosphere-climate system. This CD-ROM presents IMAGE 2.2 and its implementation of the six IPCC SRES scenarios. The complete causality chain (from pressure, to state, to impacts, including feedbacks) is modelled by IMAGE 2.2.
Acid rain commonly has high concentrations of dissolved SO2-4, NH+4 and NO-3. Sulphuric and nitric acids are usually considered to be the acidic components, whereas ammonium has a tendency to increase the pH of rainwater1. Ammonium can be transformed to nitric acid in soil but this source of acidity is generally less important than wet and dry deposition of free acids2,3. Here we describe the occurrence of high concentrations of ammonium in canopy throughfall (rainwater falling through the tree canopy) and stemflow in woodland areas in the Netherlands, resulting in acid inputs to soils two to five times higher than those previously described for acid atmospheric deposition2-5. The ammonium is present as ammonium sulphate, which probably forms by interaction of ammonia (volatilized from manure) with sulphur dioxide (from fossil fuels), on the surfaces of vegetation. After leaching by rainwater the ammonium sulphate reaching the soil oxidizes rapidly to nitric and sulphuric acid, producing extremely low pH values (2.8-3.5) and high concentrations of dissolved aluminium in the non-calcareous soils studied. Deposition of ammonium sulphate on the surfaces of vegetation and its environmental consequences are probably most important in areas with intensive animal husbandry.
In this thesis, the central research question is: what can be the contribution of renewable energy sources to the present and future world and regional energy supply system. The focus is on wind, solar PV and biomass energy (energy crops) for electricity generation. For the assessment of the economic potential, we construct cost-supply curves. As the economic potential also depends on the way renewables are integrated in the electricity system, we also explore the overall costs of wind electricity with increasing penetration levels of the installed wind capacity into the system. The potentials of solar, wind and biomass electricity are analysed at a global and regional level, for seventeen world-regions similar as used in the IMAGE 2.2 model to make future use of the results for scenario analysis with the IMAGE 2.2 model possible. The IMAGE 2.2 model (Integrated Model to Assess the Global Environment) is developed at the National Institute of Public Health and the Environment (RIVM)). This model is one of those used for the construction and evaluation of SRES energy scenarios by the Intergovernmental Panel on Climate Change (IPCC). In summary, we can conclude that the renewable electricity sources studied in this thesis have a potential to generate several times more electricity than the present electricity demand at costs in the range of present electricity costs. Solar PV has the most significant technical potential, but is at present not available at competitive costs in grid connected options. In the longer term, costs of solar PV may come down at cost levels comparable to conventional electricity, especially in sunny areas. The costs depend in the case of biomass electricity strongly on the technological development of the agricultural sector, on the labour wages, the capital-labour ratio and the land rental costs. Costs of wind electricity are already nearly competitive and the wind electricity sector has increased considerably the last decades. However, to what extent the overall costs of wind electricity can decrease further with increasing penetration levels, depends amongst others on the available storage capacity and interconnection of the system. The spatially explicit calculations done in this study provide interesting new insights concerning the potential of renewable energy sources. This thesis considers on a grid-cell level, next to climatic characteristics, also characteristics of land-use and soil quality, when estimating the future potential of renewables. In particular for the assessment of the future potential of biomass energy, the demand for agricultural land is of high importance as these are expected to be planted at abandoned agricultural land. Land area required to generate the wind electricity potential depends on social factors, but default values in this thesis indicate that to generate 6 times the present electricity production about 1.1 Gha is needed, about the size of China. To generate about 23 times the present electricity production with solar PV, an area of 0.23 Gha is needed, about 20% of China. To generate biomass derived electricity equal to 5 times the present electricity production, in the A1 scenario (highest potential) at abandoned agricultural area, about 1.3 Gha is needed, about 120% of the area of China.
Air quality, ecosystem exposure to nitrogen deposition, and climate change are intimately coupled problems: we assess changes in the global atmospheric environment between 2000 and 2030 using 26 state-of-the-art global atmospheric chemistry models and three different emissions scenarios. The first (CLE) scenario reflects implementation of current air quality legislation around the world, while the second (MFR) represents a more optimistic case in which all currently feasible technologies are applied to achieve maximum emission reductions. We contrast these scenarios with the more pessimistic IPCC SRES A2 scenario. Ensemble simulations for the year 2000 are consistent among models and show a reasonable agreement with surface ozone, wet deposition, and NO2 satellite observations. Large parts of the world are currently exposed to high ozone concentrations and high deposition of nitrogen to ecosystems. By 2030, global surface ozone is calculated to increase globally by 1.5 +/- 1.2 ppb (CLE) and 4.3 +/- 2.2 ppb (A2), using the ensemble mean model results and associated +/-1 sigma standard deviations. Only the progressive MFR scenario will reduce ozone, by -2.3 +/- 1.1 ppb. Climate change is expected to modify surface ozone by -0.8 +/- 0.6 ppb, with larger decreases over sea than over land. Radiative forcing by ozone increases by 63 +/- 15 and 155 +/- 37 mW m(-2) for CLE and A2, respectively, and decreases by -45 +/- 15 mW m(-2) for MFR. We compute that at present 10.1% of the global natural terrestrial ecosystems are exposed to nitrogen deposition above a critical load of 1 g N m(-2) yr(-1). These percentages increase by 2030 to 15.8% (CLE), 10.5% (MFR), and 25% (A2). This study shows the importance of enforcing current worldwide air quality legislation and the major benefits of going further. Nonattainment of these air quality policy objectives, such as expressed by the SRES-A2 scenario, would further degrade the global atmospheric environment.
Increased production of biomass for energy has the potential to offset substantial use of fossil fuels, but it also has the potential to threaten conservation areas, pollute water resources and decrease food security. The net effect of biomass energy agriculture on climate could be either cooling or warming, depending on the crop, the technology for converting biomass into useable energy, and the difference in carbon stocks and reflectance of solar radiation between the biomass crop and the pre-existing vegetation. The area with the greatest potential for yielding biomass energy that reduces net warming and avoids competition with food production is land that was previously used for agriculture or pasture but that has been abandoned and not converted to forest or urban areas. At the global scale, potential above-ground plant growth on these abandoned lands has an energy content representing approximately 5% of world primary energy consumption in 2006. The global potential for biomass energy production is large in absolute terms, but it is not enough to replace more than a few percent of current fossil fuel usage. Increasing biomass energy production beyond this level would probably reduce food security and exacerbate forcing of climate change.
Increasing energy use, climate change, and carbon dioxide (CO2) emissions from fossil fuels make switching to low-carbon fuels a high priority. Biofuels are a potential low-carbon energy
source, but whether biofuels offer carbon savings depends on how they are produced. Converting rainforests, peatlands, savannas,
or grasslands to produce food crop–based biofuels in Brazil, Southeast Asia, and the United States creates a “biofuel carbon
debt” by releasing 17 to 420 times more CO2 than the annual greenhouse gas (GHG) reductions that these biofuels would provide by displacing fossil fuels. In contrast,
biofuels made from waste biomass or from biomass grown on degraded and abandoned agricultural lands planted with perennials
incur little or no carbon debt and can offer immediate and sustained GHG advantages.
Corn cultivation in the United States is expected to increase to meet demand for ethanol. Nitrogen leaching from fertilized corn fields to the Mississippi–Atchafalaya River system is a primary cause of the bottom-water hypoxia that develops on the continental shelf of the northern Gulf of Mexico each summer. In this study, we combine agricultural land use scenarios with physically based models of terrestrial and aquatic nitrogen to examine the effect of present and future expansion of corn-based ethanol production on nitrogen export by the Mississippi and Atchafalaya Rivers to the Gulf of Mexico. The results show that the increase in corn cultivation required to meet the goal of 15–36 billion gallons of renewable fuels by the year 2022 suggested by a recent U.S. Senate energy policy would increase the annual average flux of dissolved inorganic nitrogen (DIN) export by the Mississippi and Atchafalaya Rivers by 10–34%. Generating 15 billion gallons of corn-based ethanol by the year 2022 will increase the odds that annual DIN export exceeds the target set for reducing hypoxia in the Gulf of Mexico to >95%. Examination of extreme mitigation options shows that expanding corn-based ethanol production would make the already difficult challenges of reducing nitrogen export to the Gulf of Mexico and the extent of hypoxia practically impossible without large shifts in food production and agricultural management.
• Gulf of Mexico
• hypoxia
• nitrogen cycling
• biofuels
• agriculture
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